Contamination control, including particulate monitoring, plays a role in the manufacturing processes of several industries. These industries require clean rooms or clean zones with active air filtration and require the supply of clean raw materials such as process gases, de-ionized water, chemicals, and substrates. In the pharmaceutical industry, the Food and Drug Administration requires particulate monitoring because of the correlation between detected particles in an aseptic environment and viable particles that contaminate the product produced.
Recent attention has been given to the monitoring and detection of biological agents. If aerosolized agents (biological particles) are introduced into an environment and are within the respirable range of particle sizes, then the biological particles may deposit in human lungs resulting in illness or death.
Biological contamination can occur not only in open air, but also in confined spaces, such as postal handling equipment, aircraft, hospitals, water supplies, and air ducts. Minimizing the introduction of biological particles in an environment requires the fast detection of pathogens. Laser-induced fluorescence (“LIF”) of fluorescent biological substances (biofluorophores) provides a real-time technique for identifying the potential presence of airborne pathogens such as aerosolized bacterial spores and viruses. Biofluorophores significant to LIF include, but are not limited to, tryptophan, NADH, and riboflavin or other flavinoids.
Assemblies that have been used in sample preparation for detection of particles include pre-filter scalpers and concentrators. A scalper may be a device used to separate out particles in the sample air stream, for example, based on particle size. A concentrator may be used to increase particle concentration by increasing the number of particles by volume in the sample air stream.
One category of scalpers that has been used to separate out large particles from particle-laden air streams is vortex separators, also known as cyclone separators. A classical vortex separator device has a settling chamber in the form of a cylinder. The particle-laden air sample enters the cylinder tangentially and spirals downward in the chamber in a vortex due to the pressure distribution in the chamber and chamber geometry. As the particle-laden air stream travels around the vortex, the larger particles are pushed toward the chamber walls due to centrifugal forces. Below the cylindrical portion of the chamber is a conical section, which causes the vortex diameter to decrease until the majority of the spinning air stream spins up the center of the chamber in an inner vortex to the vortex finder. The smaller particles, having less mass, get caught in the suction of the inner vortex that exits the vortex finder. Larger particles that are centrifuged to the wall of the chamber are not part of the sample that exits the vortex finder.